Thermostable _D-Amino Acid Aminotransferase from a Thermophilic Bacillus sp. SK-1, Symbiont of a Thermophilic Symbiobacterium sp. SC-1:Gene Cloning and Sequence Determination

　

Seung-Pyo HONG^*a, Seung-Goo LEE^a, Mi-Sun KWAK^a, Yoon-Ho CHOI^a, Nobuyoshi ESAKI^b, Kenji SODA^c, and Moon-Hee SUNG^a

　

^a Microbial Conversion Research Unit, Korea Research Institute of Bioscience, and Biotechnology (KRIBB), P.O.BOX 115, Yusong, Taejon 305-600, Korea

^b Laboratory of Microbial Biochemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611, Japan

^c Department of Biotechnology, Kansai University, 3-3-35, Yamate-cho, Suita-shi, Osaka 564, Japan

　

The gene encoding _D-amino acid aminotransferase of a thermophilic Bacillus sp. SK-1, symbiont of a thermophilic Symbiobacterium sp. SC-1, has been cloned and expressed efficiently in Escherichia coli. The primary structure of the enzyme was deduced from nucleotide sequences of the gene and confirmed by N-terminal amino acid sequence and analysis of C-terminal amino acid residues of the gene product. The gene consists of 864 base pairs encoding a protein of 288 amino acid residues; the molecular mass of the enzyme subunit is estimated to be 33,135 daltons. Comparison of the amino acid sequence with those of _D-amino acid aminotransferases from other Bacillus species revealed low overall similarities. Several amino acid residues conserved in all the compared sequences include those that have been reported to participate in the binding of the coenzyme in the three-dimensional structure of the Bacillus species YM- 1 emzyme.

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